The objective of the proposed research is unified, quantitative theory of binaural interaction that is applicable to a wide variety of binaural phenomena and that is consistent with neurophysiological data on the auditory system. This research, which is a direct outgrowth of past work by our research group, and which involves large amounts of both psychophysical experimentation and theoretical modeling, will include further studies of both interaural sensitivity and subjective attributes of the binaural image space. The proposed activities will capitalize on our highly-developed laboratory facilities, on modeling techniques derived from statistical communicatons theory, and on the systematic physiological data now available describing the peripheral transduction from acoustic waveforms to auditory-nerve firing patterns. The research is primarily concerned with the development of a mathematical description of a central processor that operates on the firing pattens as inputs and leads to psychophysical performance equivalent to that exhibited by human listeners. Most of the specific problem areas addressed by the research concern the incorporation of subjective attributes into the theory and the interaction of interaural time difference with interaural intensity difference. Included among these problem areas are sensitivity to simultaneous incremental changes in interaural time and intensity difference, the effect of reference interaural time and intensity difference, the effect of reference interaural time and intensity difference on this sensitivity, the ability to discriminate between time difference and intensity difference, and the location and spatial form of the subjective image for various combinations of time difference and amplitude difference. To the extent that this research is successful, it will provide a major improvement in our understanding of binaural interaction, and therefore, since binaural interaction plays a crucial role in auditory function, in our understanding of audition.